Chemistry of Chromium Detection
Detecting chromium ions through various reactions like adding NaOH, NH4OH, Na2CO3, and K2CO3. Exploring the distinct reactions of Cr(III) and anions like chromate and dichromate in solution.
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Chemistry of Chromium (1)Detecting chromium triple ion (Cr3+) Chromium triple solution can be prepared by dissolving CrCl3.6H2O in water to form green solution resulted from the complex ion [Cr(H2O)6]3+ CrCl3.6H2O + H2O Dark green solid This aqueous ion has an acidic characteristic in water: [Cr(H2O)6]3++ H2O [Cr(H2O)5OH]2++ H2O+ [Cr(H2O)6]3+ Green clear solution pKa= 4
This ion can be abbreviated into (Cr3+) to carry out the following detections: 1)Put (10) drops of [Cr(H2O)6]3+solution in a test tube, add (2) drops of NaOH, and observe the change, then add more of the detector and observe the change. then add (2) drops of H2O2, observe the change, and heat the solution for 5 mints. and observe the change and write down your notices after each addition.
2) Put (10) drops of [Cr(H2O)6]3+in a second test tube, add (2) drops of NH4OH, then add more of the a ammoni conc. and observe the change. Write down your notices in both cases.
M2+,M3+ : 3) Put (10) drops of [Cr(H2O)6]3+in a third test tube, add (2) drops of Na2CO3or K2CO3, observe the change and write down your notices.
Question: 1) What is the distinguishable detection of Cr(III) Ion? 2) Write all question ?
(2) Detecting anions A balance happens for the both (yellow) and Dichromate (orange) when a quantity of K2CrO4and K2Cr2O7is dissolved in water, according to the following equation: CrO42 (aq)+ 2H+ Chromate and dichromate solutions are prepared by dissolving Na2CrO4, Na2Cr2O7, K2CrO4, or K2Cr2O7in water to compose a yellow or orange solution. anions Chromate Cr2O72 (aq)+ H2O (L)
: 1) Put (10) drops of in a test tube and add (2) drops of NaOH, observe the change and write down your notices. 2) Put (10) drops of in a second test tube, add (2) drops of HCl, observe the change and write down your notices. 3) Put (10) drops of in a third test tube, add (2) drops of Pb(NO3)2or Ba(NO3)2, observe the change and write down your notices. 4) Put (10) drops of in a test tube, add (2) drops of NaOH, observe the change and write down your notices. 5) Put (10) drops of in a second test tube, add (2) drops of HCl, observe the change and write down your notices. 6) Put (10) drops of in a third test tube, add (2) drops of Pb(NO3)2or Ba(NO3)2, observe the change and write down your notices.
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Questions 1) What happen when HCl is added to ion chromate ? 2) What happen when NaOH is added to ion chromate ? 3) What happen when Pb(NO3)2or Ba(NO3)2is added to ions? 4) This equation TRUE OR FALS?
(3)Preparation of Chromic Oxide (Cr2O3) Gradually put (1) gr of the orange ammonium dichromate (NH4)2Cr2O7in a crucible on flame, very soon you will see flash at each addition. Pull the flame away from the bowl when the flashing happens. Return the flame again after flash end until the dichromate quantity is decomposed. Reaction Equation: (NH4)2Cr2O7 N2 + Cr2O3+ 4H2O
Questions: 1)What the flash means? 2)Calculate the product percentage. 3)Why dichromate is gradually added? 4)What is the principle of this reaction?
